First off, thanks for the many suggestions from the experienced GMs here at enworld!
I incorporated on the fly battles without a mat, asking the party to describe actions and adjudacating as needed but not too much. They had scouted the area with an invisible companion (brain in a jar reskinned as the animated bust of an old man) so they had a very decent top down map of the orc camp.
Regarding Skill Challenges
There was never an actual 4e skill challenge. Rather I took a simulationist approach to the story telling. If they climbed I would describe the possibility of ledges to break it in to smaller chunks. The players had to use a lead climer to set pittons (Durn) and then climb up. At 20 and 50 feet there were ledges for them to rest at. Total climb, 100 feet.
The climb had some tense moments. The bard fell twice. One with a critical failure. Rolling a critical fumble while climbing can mean certain death. Why? That is so anticlimactic. The players feel screwed. So instead the assassin used an action point (he had 1 saved) and spent a healing surge to negotiate that he shadow stepped out into Durns shadow and in to the shadow of the plummetting bard, grabbing her from mid-air and latching on to the rope with a solid acrobatics check. The bard had a chance to roll athletics to cling to him as he appeared out of her shadow. Success.
They finally made it to the top, with Durn rolling a nat20 on athletics to literally pull all three party members the last 50 feet after the near death of the Bard and failed checks by the heavilly armored warlord. Reminded me of Mr. Stallone in that aweful climbing flick he did. This was basically a simulation of climbing. No tracked skill checks, just a dangerous attempt and it required some dice rolls. It may have felt like too many (10 checks per person) but I wanted it to feel like an risky choice, but rewarded by silent insertion behind the enemy lines. High risk, high reward.
I only tracked two things as skill challenges.
Crafting a Poison
The concoction of the poison by the "morally flexible" female half-elven bard and the dragonborn assassin was a series of skill checks broken in to four phases.
1. They rolled okay (avg dc success) when trying to combine the stock of chemicals and powders the Orc Shaman had in his hut. I counted it as a single success but it would only make the Orcs really sick and effect combat if they had to face all of them. They wanted to kill the Orcs though.
2. The assassin knew of a nasty local herb but did not know what it looked like (avg. dc success). A history check by Durn's paladin of the red knight brought a story to mind involving that herb. His character loves to tell obscure stories. So he told the folk story of the herb as part of the successful roll. Another success, and a critical one. if they had failed the potion would not have gotten any better.
3. They all searched for the herb in the woods. Someone rolled a 19, and despite not being trained, they found some of the stuff. Success.
4. Then the Assassin had to extract and reduce the toxic agent. He rolled well on his Thievery check (25+ at level 4). Success. The potion was put together.
5. Finally, I rolled a percentile to grant a total effectiveness for the poison. This was kept from the party. I tend to roll openly, but this one was pretty critical. A 97%! That was some nasty poison. Super Success but they didn't know it yet.
They could have failed or succeeded at any point, or had a moderate success. I don't think the normal 8 before 3 deal would have worked because they didn't all have something to do and I think forcing everyone to roll each round would have slowed it down and made the process feel more contrived. As it was they each contributed when it made the most sense. I believe the Warlord was the one that rolled the high nature check, his sole contribution to that challenge.
Avoiding Notice
I rolled perception checks every time they did something that could have caught a guards eye. You might call this a skill challenge for the Orcs. They needed three successess before the party slaughtered them. They caught on after the posioned food was distributed and pulled their remaining forces to the top of the rock formations.
Eventually the bard and assassin sneaked past the Orc perimeter line. The bard tripped an alarm wire and bells tinkled (stolen from elves no doubt). The two hid in a pile of refuse the Orcs had in the middle of camp. Lazy, filthy creatures Orcs. This was the 3rd time that game that the assassin saved the bards bacon and highlights one way I was using natural 1s. Here I probably asked them to roll too many times. THey had made the poison, and just had to get it in to the cook pot. The bard had her unseen servant drag the pot across the ground and dump it in. A distracted Orc contigent didn't notice but another 1 at the end meant the poison pot ended in the cook pot. She asked if she could have the Servant take it out. I ruled it could fling it on the refuse pile and the assassin could catch it. That received some eyebrow raises. Later one player said it felt like i was making them roll until they failed. This was not my intention but a learning experience none-the-less. That section took too long.
The super effective poison did it's work in 3 hours time. The orcs at the base camp were all dead as door nails. The posion must have covered the flavor of typically rancid meat because they all took seconds. The party armed the slaves and doused two torches at the edge of the camp to help cover their escape (orc perception check failed to notice this from the top of the rock formations). They readied to free the slaves into the woods. I had to remind them they were in a very dangerous swamp. Survival was unlikely. THey chose to bring the slaves along.
They moved up to the top of the rock formations where the Orcs had their fortified positions. A lot of dead orcs. Silence. More improvised checks by the Assassin to take out two lone guards in a Watch tower . He then peaked in to a large tent and saw the human Big Bad and two head orcs. (half-orc death shaman and scarthane in the book, both elites and level 6 courtesy of Masterplan).
Something triggered the Orcs ambush. The rope bridge was cut behind them. the bard responded by cutting the second bridge. Orc reinforcements were now stuck out of reach, but the PCs and slavese were trapped at the top of a 100 foot rock formation.
Now I reached an ironic dilemma. The game had gone TOO fast. They were missing the second striker in the party (an avenger named Avok.... Because you can't spell Havok without Avok. *wince*). They had 30 minutes left and we'd already covered the murder of almost all the orcs. Two remained and the party was very low on resources. They had maybe one last fight in them before an extended rest. The plan was to have them fight a really nasty solo at the beginning of the next session. So they had to fight the Orcs. It just made sense. Sadly it would mean they would have no chance of surviving the solo, later. (fiery dragon described by durn). Oh well, go with it, right?
We rolled out the battle mat for the first time during the session. The fight was brutal. Durn the tank was knocked out round 1. Check scarthane's block. He hits like a truck and rolled high. It was a close thing, with the two leaders using all their heal powers but not their second winds. The bard got stuck in the Death Mages insect swarm so she spent a "awesome card" which requires a healing surge, to make her "Shout" destroy the swarm. Opposed Arcana checks by her and thh death mage turned out in her favor. The zone was gone and after that they party mopped them up. The final blow was a last minute Targeted for Death by the assassin that slammed the orc into the fire pit.
So now what. They have few surges, no dailies, no potions, no friends... Enter the long dead green dragon the bad guys had been messing with. The spirit of the green dragon is offended by the red flaming young wyrm that has taken up residence. He wants it dead and wants to sleep again. The bard has a psychic covnersation and the dragon who offers to lend some of its strength if they take the large spirit gem that has been imbued with his energy and destroy it in the still surging teleportation portal while the party stands inside it. We left with the party agreeing to do so.
We left it there. They earned a level, and the benefits of an extended rest. I'll still make them save against their Filth Fever when they take an actual rest later on.
Next week? What I deem to be a really difficult Solo dragon. I"ll link the stat block I came up with and request some suggestions, but that is another thread. What could have taken three-four sessions with our old approach was ccomplished in a single one. The party gladly went an extra 30 minutes over to fit in the fight. They were hungry for it! I'd say this was the most enjoyable session in months.
Thanks again all.